Evaluation of Stomatognathic Problems in Children with Osteogenesis Imperfecta (Osteogenesis Imperfecta − OI) − Preliminary Study

Abstract According to epidemiological data, muscular dysfunctions of the masticatory system occur in 15-23% of the population. Preventive examinations of functional disorders of the stomatognathic system are, therefore, of particular importance. A distinct group of patients exposed to dysfunctions in the area of the masticatory organ locomotor apparatus comprises those with genetic diseases characterised by disorders in collagen formation. One of such diseases is osteogenesis imperfecta (OI) and dentinogenesis imperfecta that usually goes together with the former. Aim The objective of this work was to evaluate the frequency with which particular disorders of the masticatory organ locomotor apparatus occur within the group of patients with osteogenesis imperfecta. Material and methods The study was performed on patients of the Orthopaedic Clinic of the Polish-American Paediatric Institute in Kraków. The mean age of the children was 7.9 years. In all the cases, a genetic diagnosis of OI has been confirmed. The research methods were based on an in-depth interview on family diseases, pregnancy, postnatal period, feeding, subjective assessment of dysfunctions in the stomatognathic system. An examination of the deformations in the stomatognathic system and the skeleton was conducted, as well as an examination of the trauma and tone of the jaw. The relationship between breastfeeding and swallowing and speech disorders was also evaluated. The impact of intubation on mandibular ranges was investigated. Results The results obtained were subjected to statistical analysis on the basis of which conclusions were drawn concerning disorders in the stomatognathic system which tend to occur in children with OI. The renunciation of breastfeeding significantly contributes to sucking and swallowing disorders, rumen disorders, as well as biomechanical disorders in the temporomandibular joint. A significant dependence between breastfeeding and swallowing problems was found, whereas there was no such dependence with respect to speech impediments. Conclusions The results of the research conducted led to the following conclusions: 1. Among pediatric patients with OI there are disorders in the stomatognathic system. The most common dysfunctions are: abdominal, swallowing and sucking disorders, abnormal muscle structure of the rumen and biomechanical disorders in the temporomandibular joints. Breastfeeding significantly contributes to swallowing disorders. 2. The therapeutic process involving children with OI requires the cooperation of specialists in orthopedics, pediatrics, physiotherapy, orthodontics and neurologopedics to carry out comprehensive diagnostics and treatment tailored to the individual needs of the patient. 3. In order to draw final conclusions, there is a need for more research by means of objective tools, such as EMG and a condensate recorder.


INTRODUCTION
According to epidemiological data, muscular dysfunctions of the masticatory system occur in 15-23% of the general population. As we know from many clinical studies, the percentage of patients who su er from dysfunctions in the stomatognathic system is 50-80%. Among persons su ering from symptoms of temporomandibular joint disorders, the female sex predisposes to such disorders in the proportion of 2:1 or even 3:1 [1,2]. So far studies of functional disorders in the area of the stomatognathic system have mainly been related to the adult population. ere are very few publications available concerning children. Some of the most signi cant ones include works that discuss the impact of the occlusion plane upon body posture, occlusion disorders, or displacement of impacted permanent teeth [18,19,20]. Due to low awareness among the society of the occurrence of disorders in the masticatory organ area in children and adolescents, it is recommended that educational health-promotion activities through broadlycomprehended preventive care extending to both adults and children should be undertaken. Preventive examinations of functional disorders of the stomatognathic system are of particular importance [3]. Results of screening studies suggest that the age of the persons who su er from temporomandibular joint diseases is increasingly lower [4,5].
It is also signi cant that temporomandibular joint disorders are not only limited to dysfunctions of the joint itself and its periarticular structures; they also extend to structures located far away from the source of pain. e main reasons for dysfunctions of the masticatory organ locomotor apparatus include inter alia: joint sti ness condition, mandibular injuries, increased or decreased muscle tension, body posture disorders, and a erent impulses connected with the feeling of deep pain.
A distinct group of patients exposed to dysfunction in the area of the masticatory organ locomotor apparatus comprises those with genetic diseases characterised by collagen formation disorders. One of such diseases is osteogenesis imperfecta (OI), as well as dentinogenesis imperfecta and dentin dysplasia, which accompany the former. Patients who su er from this disease reveal distorted proportions and symmetry of the body, uneven distribution of connective tissue, osteoarticular deformations, ligament laxity, vascular lesions, improper construction of auditory ossicles, neurological disorders, as well as shortened and deformed tooth roots, and thin, brittle tooth enamel. e consequence is a frequent occurrence of: lowering of the occlusion height, occlusion defects, and functional disorders of the masticatory organ.
In works devoted to this disease relatively little attention is given to the occurrence of stomatognathic problems and functional disorders of the masticatory organ, i.e. biting and chewing of foods, swallowing of foods, and joint participation in breathing and speech functions due to the crossing of the digestive tract with the respiratory tract. De nitions related to the stomatognathic system concept are presented in table I.

AIM
Assessment of the frequency of particular disorders of the masticatory organ locomotor apparatus within the group of patients with osteogenesis imperfecta, and an attempt at assessment of their impacts upon child development.

MATERIAL AND METHODS
e study included 19 children from Poradnia Ortopedyczna Polsko-Amerykańskiego Instytutu Pediatrii (UJ CM) in Kraków with genetically diagnosed osteogenesis imperfecta. A group of 20 patients with osteogenesis imperfecta was selected (one child was excluded from the study in the process due to psychomotoric disorders that made it impossible to perform the physical examination). e basic condition for a patient to qualify for the study was the diagnosis of osteogenesis imperfecta . Another selection criterion was the patient's age which had to range from 1 to 18 years. e criterion that excluded the patient from the test group was the coexistence of a serious psychomotoric disability that made it impossible to perform the physical examination. e above-mentioned patient selection criteria were used to restrict the number of any disturbance factors and in this way achieve the best possible homogeneity of the group. e study included children whose parents expressed their written consent to perform the necessary procedures upon having received complete information on the project. Children's medical histories were gathered, covering: diseases that occurred in their families, the course of pregnancy, perinatal and breastfeeding disorders.
Our own questionnaire form was also lled in, covering: the course of the disease and the current state of the child's health, subjective assessment of dysfunctions in the stomatognathic system, and assessment of pain.
Photos in 5 views were taken to illustrate some visible anomalies in the osteoarticular system and structural anomalies in the facial skeleton ( Fig. 1-5).

Stomatognathic system
A morpho-funcƟonal whole that consists of dental, osteoarƟcular, muscular structures and glands, connected with one another by means of blood vessels, lymphaƟc vessels and nerve fibres of the somaƟc and vegetaƟve system; the stomatognathic system consists of such elements as: the oral cavity, teeth, the jaw, the mandible, the pharynx, and structures connected with chewing, swallowing and speech funcƟons
Dental organ Teeth including periodonƟum     Table II. The occurrence of the characterisƟc overall and in subgroups of subjects, by gender, tested in percentages. Tabela II. Występowanie badanej cechy u pacjentów ogółem oraz w podgrupach z uwzględnieniem płci, w procentach.

Ryc. 5. Dysplazja zębiny ze zniekształceniem kości czaszki u 5-letniego chłopca z OI. (źródło własne)
e physical examination comprised: A. postural analysis according to Langlade, B. assessment of bone deformations in the stomatognathic system and skeletal deformations, C. joints, muscles of the masticatory organ, of the neck, and the upper limb girdle, D. examination concerning the occurrence of crepitation, cracking noises, E. examination of the path and range of mandible movements in all their axes (the maximum mandible retraction range was measured using a rule calibrated with the accuracy of 1 mm. Both measurements were repeated three times, in several-minute-long time intervals); a front graph was drawn for each patient. e initial examination of the patient aimed to make an initial assessment of the defects in their body posture and the way they move, including the position of the head and the shoulder girdle. Simultaneously with observation, the above-mentioned medical history was examined.
Information upon the course of each pregnancy, the postnatal period, and symptoms of masticatory organ locomotor apparatus dysfunctions and other data which were obtained using the questionnaire and medical history is placed in table II, splitting respondents by their sex and age. e averaged results of mandible movement range measurements, in total and for each age group, are presented in table III. e patient took a free sitting position with the head turned at the angle of 70° in relation to the base plane, and the patient' s facial symmetry, the function of mimic muscles, and mandible movements while speaking were examined.   Periarticular structures of temporomandibular joints were examined by palpation (outside and inside the oral cavity), as were masticatory suboccipital muscles and pectoral muscles. Examination was performed of: the tension degree of the examined muscles; the increased muscle attachment tenderness, enlargements, and the morphological structure of bellies. Examination of the range of mandible movements in all their axes comprised: retraction and protraction movements, protrusion movements and translation movements. Mandible lowering and li ing movements were assessed using the objecti ed metric method. e mandible retraction range was examined in more depth by performing two measurements: maximum free retraction, i.e. the distance between incisal edges of the teeth and the occlusion line (upon having marked it at the lower incisors). e mandible retraction range was measured using a ruler that was calibrated with the accuracy of 1 mm.

RESULTS
e results obtained were subjected to a statistical analysis to determine the relationship between the tested features. Chi square tests for independence, t-test for independent samples, and one-way analysis of variance were used. Dependencies between individual features were analyzed using Statistica. In all the tests carried out, a signi cance level of 0.05 was adopted.
Information on the course of pregnancy, postnatal period and symptoms of dysfunction of the chewing motion system and other data obtained through interview and questionnaire are presented in table II, taking into account the distribution of the tests by gender. e data show that most of the children with OI were breastfed. Renunciation of breastfeeding signi cantly contributes to swallowing disorders. 42% of the subjects had suction disorders and 15% speech disorders. It is also interesting that only half of the study group are children born by caesarean section. In the area of masticatory dysfunction 15% of the children have had teeth grinding and 15% teeth clenching, 5% headaches. e mandibular vein was a ected by 85% of the majority of children tested.
e averaged results of the measurements of the mandibular movements in general and in the age groups are presented in  not di er from functional norms, although there is a tendency for hypermobility in temporomandibular joints, also dehydration, protuberance and translation. e results obtained were subjected to statistical analysis in order to determine the relationships between the features examined. Inter alia, chi square tests of independence, Student's t test for independent samples, and single variant analysis were used.
In order to examine breastfeeding e ects upon swallowing and speech disorders, the chi square test of independence was used. Based upon the test conducted, a statistically signi cant relationship (p=0.0028) was identi ed between breastfeeding and swallowing disorders. Breastfeeding discontinuation signi cantly contributed to the occurrence of swallowing disorders in children with OI (tab. IV). Based upon the test conducted, no occurrence of statistically signi cant relationship (p=0.7642) was found between breastfeeding and speech disorders (tab. V).
Intubation e ects upon mandible movement ranges due to frequent surgery treatments in children with OI were also examined. Student's t test for independent samples was used. Based upon the test conducted, no signi cant di erence was found in retraction, protrusion and lateral movements depending on the intubation type used (tab. VI). Table VII presents the results of the analysis of age variance on the extent of the jaw movement. e joints' range of movement depends on the age of the child.

DISCUSSION
To-date the study results point to the fact that functional disorders in the area of the stomatognathic system in particular pertain to the adult population. Meta-analysis of 51 studies performed by De Kanter on the frequency in which these disorders occur con rmed that functional disorders in the stomatognathic system were felt by 30% of patients, whereas they were identi ed in 44% of the patients in clinical studies [6].
e Study Health Project conducted in Pomerania, which comprised stomatognathic system examinations, showed that approx. 49% of the respondents had at least one symptom that pointed to temporomandibular joint disorders (25%) or masticatory muscle hypersensitivity (15%) [6,8].
Only few publications are available on the problem we discuss here. Hence, based upon the results of our own initial examinations, it should be considered that that OI-type diseases pose a serious risk factor for the occurrence of the above-mentioned dysfunctions. Most studies are devoted to masticatory organ locomotor apparatus dysfunctions in healthy children and adolescents (who are free from genetic diseases). In her systematic review of literature, Dąbrowska-Gontarczyk presented the epidemiology of bruxism in children and adolescents in the years 2000-2012. As a result of the analysis of 50 publications on randomised clinical studies, cohort studies and clinical/control studies, it was concluded that the frequency of bruxism occurring in developmental age patients in the general population ranged from 1.5% to 90%. Studies were most frequently conducted on children from 3 to 18 years old. e analysis revealed high discrepancies in the results of studies conducted by di erent authors, which may be due to the research tools used, i.e. mainly a questionnaire that was lled in by parents and guardians. Clinical evaluation of patients was only conducted in 21 studies. Among symptoms that accompanied bruxism, mainly psychological factors were identi ed, i.e.: stress, depression, neuroticism. Plentiful publications emphasised the co-occurrence of bruxism with ADHD, autism, and sleeping disorders [10]. e share of genetic factors, i.e. the occurrence of family bruxism, was presented in works by Seraj, Chejfetz and other authors [9][10][11][12][13][14], although these scholars did not mention any occurrence of bruxism in genetic diseases such as osteogenesis imperfecta. Other studies performed by Nekora-Azak (2006) on a group of eighteen-year-olds for a representative population of Istambul revealed pain in the mandibular area (31%), clenching the jaw and grinding the teeth (23%), cracking noises in the temporomandibular joint (23.7%). A higher frequency of signs (45-86%) than symptoms (14-36%) of irregularities in the masticatory organ locomotor apparatus are disclosed by the results of studies conducted earlier by:  [6].
According to the studies by Chłapowska (2004), Kalinowska and Gołębiewska (2008) performed on Polish children, the age of persons who su er from the temporomandibular joint condition is decreasing. is is indicated by screening and clinical studies. Studies by Alamoudi (1998) conducted on children aged 3-7 years in Saudi Arabia, revealed disorders in 16.53% of the cases, whereas the most frequently identi ed symptoms were acoustic symptoms from temporomandibular joints (7.8%), and muscle tenderness (6.77%) [6]. e results obtained from various epidemiological studies concerning the frequency with which signs and symptoms of temporomandibular disorders occur in children and teenagers elaborated by Feteih (2006) unveil high cross-population diversi cation. e highest rates in the range of 50-80% were identi ed in Germany, Poland, and Sweden; slightly lower, i.e. 30-50% in the United States, Israel, and Finland; and the lowest, i.e. below 30%, in the Netherlands, Japan, China, Bogota, and Saudi Arabia [8]. Interview surveys conducted in Boston among the parents and guardians of children up to the age of 17 showed that bruxism occurred in 38% of young persons, and functional disorders in 5% [10]. Swedish studies conducted in the years 1983, 1993, and 2003 proved that the occurrence of symptoms from temporomandibular joints was growing together with the respondents' age. In children aged 3 and 5, symptoms occurred very rarely, whereas more than 50% of children aged 10 and 15 showed one symptom of temporomandibular joint disorder or more [6].
Very few authors have discussed the issue of functional disorders of the masticatory organ in genetic diseases. ese are mainly focused on Down syndrome [15,17]. In the work by Młynarska-Zduniak, it was concluded that as many as 94% of the patients revealed masticatory organ dysfunctions within the group of 284 patients with Down syndrome. In systemic diseases, it is only possible to nd descriptions of cases in children, in whom muscular dysfunctions of the masticatory system and morphological lesions occur too [21,22].
In our own studies, besides swallowing disorders, bruxism was diagnosed in 15% of the cases in children with osteogenesis imperfecta, although we plan to perform studies on a larger group in order to determine the frequency and type of occurrence of other masticatory organ dysfunctions in children with OI.
Stomatognathic system dysfunctions in children constitute a significant therapeutic problem for physiotherapists and neurological speech therapists, as well as ear doctors, dentists, and orthopaedic surgeons.
In children with osteogenesis imperfecta, rehabilitation problems are highly complex due to the hazard of sprains and fractures occurring for any minor reason. Besides early physiotherapy and neurological speech therapy intervention, breastfeeding seems to be a signi cant factor, as, to a large degree, it contributes both to the appropriate development of the masticatory organ muscles and to the structure and biomechanics of the temporomandibular joint itself, as demonstrated in our own studies.
It seems necessary to perform studies on a larger group in order to draw any binding conclusions. More attention should also be paid to adaptive mechanisms and bone tissue plasticity in the aspect of intubation and lack of in uence upon the functioning of the stomatognathic system in the studied group. Due to the necessity to improve the quality of life of patients with OI in the stomatognathic aspect, a mouth-and-face improvement programme should be created for this group of patients with special attention being paid to dysphagia.

CONCLUSIONS
Disorders in the stomatognathic system occur among paediatric patients with OI. e most frequently occurring dysfunctions include: sucking and swallowing disorders, improper structure of the masseter muscle, and biomechanical temporomandibular joint disorders (including inappropriate mandibular path, subluxation, and temporomandibular hypermobility of the joint). e healing process covering children with OI requires collaboration between specialists in orthopaedics, paediatrics, physiotherapy, orthodontics and neurological speech therapy, so that comprehensive diagnostics can be conducted, as well as therapy adjusted to individual patients' needs.
Further studies are planned using objective tools, such as EMG and condylography records, to be able to draw some more binding conclusions.